Multiprotocol Label Switching (MPLS) protocol is an IETF-defined protocol that overcomes some of the shortcomings of Internet Protocol-based networks. In accordance with MPLS, routers within an Internet Protocol (IP) network construct multiple label switch paths (LSPs). Packets are assigned labels that are used by the routers to direct packets along particular paths through a network. MPLS provides traffic engineering, bandwidth management, and quality of service to IP networks. For these reasons, MPLS is increasingly being used within service provider core networks, edge networks and even large enterprise networks.
In some case, MPLS is used to create an “overlay network” of LSPs that can be viewed as logically layered upon one or more packet-based networks. Overlay networks have also been proposed as a way to improve Internet routing, such as through quality of service guarantees to achieve higher-quality streaming media.
One type of overlay network is a meshed point-to-multi-point (P2MP) MPLS overlay network, which includes a plurality of LSPs defined between an ingress node and a plurality of egress nodes. Traffic is forwarded from the ingress node to the egress nodes along the paths.
In a conventional routed network, a router makes routing decisions to forward traffic from a source system to a destination system. The router relies on routing protocols to communicate with other routing devices to learn a topology of the network and make packet forwarding decisions. Based on information within each packet, the router selects a “next hop” and forwards the packet out on an outbound physical link coupling the router to the selected next hop router. In some cases the router attempts to load balance when forwarding packets to the next hop routers, i.e., the neighboring routers coupled to its outgoing physical links. For example, the router may choose the lowest cost physical link when selecting the next hop.